Biologically active metabolites of the marine actinobacteria

This review systematically data on the chemical structure and biological activity of metabolites of obligate and facultative marine actinobacteria, published from 2000 to 2007. We discuss some structural features of the five groups of metabolites related to macrolides and compounds containing lactone, quinone and diketopiperazine residues, cyclic peptides, alkaloids, and compounds of mixed biosynthesis. Survey shows a large chemical diversity of metabolites actinobacteria isolated from marine environment. It is shown that, along with metabolites, identical to previously isolated from terrestrial actinobacteria, marine actinobacteria synthesize unknown compounds not found in other natural sources, including micro organisms. Perhaps the biosynthesis of new chemotypes bioactive compounds in marine actinobacteria is one manifestation of chemical adaptation of microorganisms to environmental conditions at sea. Review stresses the importance of the chemical study of metabolites of marine actinobacteria. These studies are aimed at obtaining new data on marine microorganisms producers of biologically active compounds and chemical structure and biological activity of new low-molecular bioregulators of natural origin.     

Overview of the chemical ecology of benthic marine invertebrates along the western Antarctic peninsula

Thirteen years ago in a review that appeared in the American Zoologist, we presented the first survey of the chemical and ecological bioactivity of Antarctic shallow-water marine invertebrates. In essence, we reported that despite theoretical predictions to the contrary the incidence of chemical defenses among sessile and sluggish Antarctic marine invertebrates was widespread. Since that time we and others have significantly expanded upon the base of knowledge of Antarctic marine invertebrates' chemical ecology, both from the perspective of examining marine invertebrates in new, distinct geographic provinces, as well as broadening the evaluation of the ecological significance of secondary metabolites. Importantly, many of these studies have been framed within established theoretical constructs, particularly the Optimal Defense Theory. In the present article, we review the current knowledge of chemical ecology of benthic marine invertebrates comprising communities along the Western Antarctic Peninsula (WAP), a region of Antarctica that is both physically and biologically distinct from the rest of the continent. Our overview indicates that, similar to other regions of Antarctica, anti-predator chemical defenses are widespread among species occurring along the WAP. In some groups, such as the sponges, the incidence of chemical defenses against predation is comparable to, or even slightly higher than, that found in tropical marine systems. While there is substantial knowledge of the chemical defenses of benthic marine invertebrates against predators, much less is known about chemical anti-foulants. The sole survey conducted to date suggests that secondary metabolites in benthic sponges are likely to be important in the prevention of fouling by benthic diatoms, yet generally lack activity against marine bacteria. Our understanding of the sensory ecology of Antarctic benthic marine invertebrates, despite its great potential, remains in its infancy. For example, along the WAP, community-level non-consumptive effects occur when amphipods chemically sense fish predators and respond by seeking refuge in chemically-defended macroalgae. Such interactions may be important in releasing amphipods from predation pressure and facilitating their unusually high abundances along the WAP. Moreover, recent studies on the sensory biology of the Antarctic keystone sea star Odontaster validus indicate that chemotactile-mediated interactions between conspecifics and other sympatric predatory sea stars may have significant ramifications in structuring community dynamics. Finally, from a global environmental perspective, understanding how chemical ecology structures marine benthic communities along the WAP must increasingly be viewed in the context of the dramatic impacts of rapid climatic change now occurring in this biogeographic region.     

Highly acidic glycans from sea cucumbers. Isolation and fractionation of fucose-rich sulfated polysaccharides from the body wall of Ludwigothurea grisea

The body wall of the sea cucumber contains high amounts of sulfated glycans, which differ in structure from glycosaminoglycans of animal tissues and also from the fucose-rich sulfated polysaccharides isolated from marine algae and from the jelly coat of sea urchin eggs. In Ludwigothurea grisea, glycans can be separated into three fractions which differ in molecular mass and chemical composition. The fraction containing a high-molecular-mass component has a high proportion of fucose and small amounts of amino sugars, whereas another fraction contains primarily a sulfated fucan. The third fraction, which represents the major portion of the sea cucumber polysaccharides, contains besides fucose, approximately equimolar proportions of glucuronic acid and amino sugars, and has a sulfate content higher than that in the other two fractions. Both D and L-isomers of fucose are found in these polysaccharides, and the sulfate is linked to the O-3 position of the fucose residues. The attachment position of the sulfate groups to the glucuronic acid units and amino sugars is still undetermined. It is possible that these compounds are involved in maintaining the integrity of the sea cucumber's body wall, in analogy with the role of other macromolecules in the vertebrate connective tissue.     

RNA viruses in the sea

Viruses are ubiquitous in the sea and appear to outnumber all other forms of marine life by at least an order of magnitude. Through selective infection, viruses influence nutrient cycling, community structure, and evolution in the ocean. Over the past 20 years we have learned a great deal about the diversity and ecology of the viruses that constitute the marine virioplankton, but until recently the emphasis has been on DNA viruses. Along with expanding knowledge about RNA viruses that infect important marine animals, recent isolations of RNA viruses that infect single-celled eukaryotes and molecular analyses of the RNA virioplankton have revealed that marine RNA viruses are novel, widespread, and genetically diverse. Discoveries in marine RNA virology are broadening our understanding of the biology, ecology, and evolution of viruses, and the epidemiology of viral diseases, but there is still much that we need to learn about the ecology and diversity of RNA viruses before we can fully appreciate their contributions to the dynamics of marine ecosystems. As a step toward making sense of how RNA viruses contribute to the extraordinary viral diversity in the sea, we summarize in this review what is currently known about RNA viruses that infect marine organisms.     

Marine Lake Mogilnoe (Kildin Island,the Barents Sea): one hundred years of solitude

Lake Mogilnoe (Kildin Island, the Barents Sea) is a marine stratified lake, a refuge for landlocked populations of marine organisms. Unlike other known marine lakes from polar areas, which communicate with the sea by water percolation at the surface, Mogilnoe has a subterranean connection with the sea like tropical and subtropical anchialine lakes. Similarly to some other marine lakes, Mogilnoe has traditionally been considered to be biologically isolated from the sea and subject to little change. We review the current status of the physical features, zooplankton and benthos of Mogilnoe and trace changes that have occurred in the lake since the start of observations in 1894. The anaerobic bottom water layer has expanded by 100 %, while the upper freshwater layer has diminished by 40 %. The species diversity of zooplankton and macrobenthos has halved. The occurrence of Atlantic cod likens Mogilnoe to some other Arctic marine lakes while the presence of large flocks of sea anemones, scyphomedusae and suberitid sponges makes it similar to tropical anchialine lakes. Lake Mogilnoe is not entirely biologically isolated; accidental introduction of species from the sea does occur. We argue that the idealised model of an isolated steady-state ecosystem can be applied to a marine lake with caution. A model of fluctuating abiotic environment and partial biological isolation portrays the real situation better.     

Seascape genetics of a globally distributed, highly mobile marine mammal: the short-beaked common dolphin (genus Delphinus)

Identifying which factors shape the distribution of intraspecific genetic diversity is central in evolutionary and conservation biology. In the marine realm, the absence of obvious barriers to dispersal can make this task more difficult. Nevertheless, recent studies have provided valuable insights into which factors may be shaping genetic structure in the world's oceans. These studies were, however, generally conducted on marine organisms with larval dispersal. Here, using a seascape genetics approach, we show that marine productivity and sea surface temperature are correlated with genetic structure in a highly mobile, widely distributed marine mammal species, the short-beaked common dolphin. Isolation by distance also appears to influence population divergence over larger geographical scales (i.e. across different ocean basins). We suggest that the relationship between environmental variables and population structure may be caused by prey behaviour, which is believed to determine common dolphins' movement patterns and preferred associations with certain oceanographic conditions. Our study highlights the role of oceanography in shaping genetic structure of a highly mobile and widely distributed top marine predator. Thus, seascape genetic studies can potentially track the biological effects of ongoing climate-change at oceanographic interfaces and also inform marine reserve design in relation to the distribution and genetic connectivity of charismatic and ecologically important megafauna.     

Sensing the sea

The development of the 'ecosystem approach' to the management of marine systems is leading to a requirement for data to be collected with greater frequency and spatial resolution than has been necessary in the past. This is being met both by the analysis of more samples (to better describe variability and temporal change) and by the deployment of instrumented platforms that gather data over long time periods. To meet these requirements in the hostile conditions at sea, a range of sensors based on physical, chemical and biological responses is being developed. These sensors have applications in laboratory analysis of collected samples, during field studies and directly in situ at remote sites for real-time observations of environmental trends. Here, we consider the role that biosensors could have in future marine monitoring programmes.     

小尺度海域空间评价单元划分技术研究——以福建省东山湾为例

科学合理的海域空间评价单元划分是各类海洋空间监测、评价、规划和管理的基础工作,对于保护海洋生态环境,实现海洋资源的可持续开发利用具有重大现实意义。然而,海洋的流动性、开放性、边界模糊性等特征,导致海洋空间评价单元划分较陆地而言更为复杂、困难。以福建省东山湾为例,提出一种适用于小尺度海域的空间评价单元划分技术方案,通过从化学属性、物理属性、生物学属性三个方面构建海域空间生态属性划分指标体系,进行空间分类评价,运用插值、叠加分析等GIS技术将东山湾划分为67个基本空间评价单元。研究结果不仅能为进一步划定东山湾海洋空间规划提供技术支持,同时为其他小尺度海域生态监测、评价、规划和管理提供科学参考。     

Historical processes and contemporary ocean currents drive genetic structure in the seagrass Thalassia hemprichii in the Indo‐Australian Archipelago

Understanding spatial patterns of gene flow and genetic structure is essential for the conservation of marine ecosystems. Contemporary ocean currents and historical isolation due to Pleistocene sea level fluctuations have been predicted to influence the genetic structure in marine populations. In the Indo‐Australian Archipelago (IAA), the world's hotspot of marine biodiversity, seagrasses are a vital component but population genetic information is very limited. Here, we reconstructed the phylogeography of the seagrass Thalassia hemprichii in the IAA based on single nucleotide polymorphisms (SNPs) and then characterized the genetic structure based on a panel of 16 microsatellite markers. We further examined the relative importance of historical isolation and contemporary ocean currents in driving the patterns of genetic structure. Results from SNPs revealed three population groups: eastern Indonesia, western Indonesia (Sunda Shelf) and Indian Ocean; while the microsatellites supported five population groups (eastern Indonesia, Sunda Shelf, Lesser Sunda, Western Australia and Indian Ocean). Both SNPs and microsatellites showed asymmetrical gene flow among population groups with a trend of southwestward migration from eastern Indonesia. Genetic diversity was generally higher in eastern Indonesia and decreased southwestward. The pattern of genetic structure and connectivity is attributed partly to the Pleistocene sea level fluctuations modified to a smaller level by contemporary ocean currents.     

我国主要海域海水养殖碳汇能力评估及其影响效应——基于我国9个沿海省份面板数据

随着海水养殖业的碳汇功能逐渐被认识和肯定,海水养殖不再单是一项经济活动,而是对环境具有正向影响的碳汇生态活动。以我国沿海9个省份为例,选取海水养殖业碳汇主要贡献的贝类和藻类海产品,并按照各自的碳汇方式对我国沿海地区2008—2015年海水养殖碳汇能力测算,进一步将9个沿海省份按照主要海域划分为渤海、黄海、东海、南海,利用LMDI模型从海水养殖的结构效应和规模效应角度分析碳汇能力的区域差异和主要影响因素。研究结果显示,黄海沿岸海水养殖碳汇能力最强,南海沿岸海水养殖的碳汇转化比例最高,规模效应与我国沿海地区海水养殖碳汇能力始终呈正相关,结构效应的作用显著但不稳定。基于上述结论,我国沿海地区碳汇养殖业应首先提升碳汇养殖技术、稳定海水养殖产量,其次注重优化养殖结构,对碳汇潜力巨大的贝类多加关注。     

Ecological and historical legacies on global diversity gradients in marine elapid snakes

Global diversity gradients have been extensively investigated for several biological groups. However, little is known whether the diversity drivers of clades that underwent major environmental transition (e.g., from land to sea) are equivalent across these different environmental settings. Here, we ask if the pattern of diversity of marine elapid snakes is determined by factors analogous to those previously found for terrestrial lineages. Through a model selection framework, we compare the effect of factors that represent five ecological and historical hypotheses. We found that both ecological and historical factors play significant roles, but habitat structure, which can be linked to historical climatic changes, was better supported. This result agrees with that previously found for terrestrial elapids, despite the different environmental pressures in terrestrial and marine contexts. Our findings suggest an equivalence of the underlying process of diversity gradient within the same lineage from land and sea, irrespective of the different physiological, spatial and historical constraints.     

景观生态学:海洋生态系统研究的一个新视角

全球海洋生态系统作为异质性的复杂巨系统是一类景观生态系统 ,具有明显的等级结构 ,因此 ,景观生态学的原理和方法完全可以应用到海洋生态学的研究中来。生态系统的尺度限制了海洋生态学向更加宏观的方向进一步发展 ,在景观的水平上 ,运用景观生态学的理论和方法可以更好地在多个尺度上开展深入广泛的研究。本文不仅讨论了海洋景观的空间异质性 ,而且就海洋景观生态学的若干研究方向进行了探讨。     

SENSORY BIOPHYSICS OF MARINE MAMMALS

The underwater existence of marine mammals has encouraged a variety of special biophysical adaptations to their environment. Their sensory and communication systems reflect the transmission properties of sea water. For example, vision is keen in spectra that penetrate water best, vocalization is broadband and used at the frequencies that appear to fit their activities best—the differences in sensory use match the intriguing variety of behavior observed for each species. To date most of the observations of animal interactions with their marine environment have dealt with sound. There has been some work on vision and studies are underway to determine animal sensitivities to hydrodynamic pressure, chemical traces and magnetic fields. The species that have been recorded to date are listed and vocalizations are generally compared. Methods for observation of sensory mechanisms are noted along with a discussion of other aspects of marine mammal biophysics including vibrissal sensation and the biophysics of movement in a fluid environment.     

Escape by inking and secreting: marine molluscs avoid predators through a rich array of chemicals and mechanisms

Inking by marine molluscs such as sea hares, cuttlefish, squid, and octopuses is a striking behavior that is ideal for neuroecological explorations. While inking is generally thought to be used in active defense against predators, experimental evidence for this view is either scant or lacks mechanistic explanations. Does ink act through the visual or chemical modality? If inking is a chemical defense, how does it function and how does it affect the chemosensory systems of predators? Does it facilitate escape not only by acting directly on predators but also by being an alarm signal for conspecifics? This review examines these issues, within a broader context of passive and active chemical defensive secretions. It focuses on recent work on mechanisms of defense by inking in sea hares (Aplysia) and extends what we have learned about sea hares to other molluscs including the cephalopods.     

Low genetic diversity in a marine nature reserve: re-evaluating diversity criteria in reserve design

Little consideration has been given to the genetic composition of populations associated with marine reserves, as reserve designation is generally to protect specific species, communities or habitats. Nevertheless, it is important to conserve genetic diversity since it provides the raw material for the maintenance of species diversity over longer, evolutionary time-scales and may also confer the basis for adaptation to environmental change. Many current marine reserves are small in size and isolated to some degree (e.g. sea loughs and offshore islands). While such features enable easier management, they may have important implications for the genetic structure of protected populations, the ability of populations to recover from local catastrophes and the potential for marine reserves to act as sources of propagules for surrounding areas. Here, we present a case study demonstrating genetic differentiation, isolation, inbreeding and reduced genetic diversity in populations of the dogwhelk Nucella lapillus in Lough Hyne Marine Nature Reserve (an isolated sea lough in southern Ireland), compared with populations on the local adjacent open coast and populations in England, Wales and France. Our study demonstrates that this sea lough is isolated from open coast populations, and highlights that there may be long-term genetic consequences of selecting reserves on the basis of isolation and ease of protection.     

Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective

Populations of sea otters, seals and sea lions have collapsed across much of southwest Alaska over the past several decades. The sea otter decline set off a trophic cascade in which the coastal marine ecosystem underwent a phase shift from kelp forests to deforested sea urchin barrens. This interaction in turn affected the distribution, abundance and productivity of numerous other species. Ecological consequences of the pinniped declines are largely unknown. Increased predation by transient (marine mammal-eating) killer whales probably caused the sea otter declines and may have caused the pinniped declines as well. Springer et al. proposed that killer whales, which purportedly fed extensively on great whales, expanded their diets to include a higher percentage of sea otters and pinnipeds following a sharp reduction in great whale numbers from post World War II industrial whaling. Critics of this hypothesis claim that great whales are not now and probably never were an important nutritional resource for killer whales. We used demographic/energetic analyses to evaluate whether or not a predator–prey system involving killer whales and the smaller marine mammals would be sustainable without some nutritional contribution from the great whales. Our results indicate that while such a system is possible, it could only exist under a narrow range of extreme conditions and is therefore highly unlikely.     

Occurrence of sulfated galactans in marine angiosperms: evolutionary implications

We report for the first time that marine angiosperms (seagrasses) possess sulfated polysaccharides, which are absent in terrestrial and freshwater plants. The structure of the sulfated polysaccharide from the seagrass Ruppia maritima was determined. It is a sulfated D-galactan composed of the following regular tetrasaccharide repeating unit: [3-beta-D-Gal-2(OSO3)-1-->4-alpha-D-Gal-1-->4-alpha-D-Gal-1-->3-beta-D-Gal-4(OSO3)-1-->]. Sulfated galactans have been described previously in red algae and in marine invertebrates (ascidians and sea urchins). The sulfated galactan from the marine angiosperm has an intermediate structure when compared with the polysaccharides from these two other groups of organisms. Like marine invertebrate galactan, it expresses a regular repeating unit with a homogenous sulfation pattern. However, seagrass galactan contains the D-enantiomer of galactose instead of the L-isomer found in marine invertebrates. Like red algae, the marine angiosperm polysaccharide contains both alpha and beta units of D-galactose; however, these units are not distributed in an alternating order, as in algal galactan. Sulfated galactan is localized in the plant cell walls, mostly in rhizomes and roots, indicative of a relationship with the absorption of nutrients and of a possible structural function. The occurrence of sulfated galactans in marine organisms may be the result of physiological adaptations, which are not correlated with phylogenetic proximity. We suggest that convergent adaptation, due to environment pressure, may explain the occurrence of sulfated galactans in many marine organisms.     

Insect Transgenesis: Mechanisms,Applications, and Ecological Safety

Abstract

Glycosylation is considered to be an important reaction for the chemical modification of compounds with useful biological activities. Glycoside hydrolases are biotechnologically attractive enzymes which can be used in synthetic reactions for assembling glycosidic linkages with absolute stereoselectivity at an anomeric centre. Most of these enzymes are commercially available but there is great interest in the search for new biocatalysts with original catalytic characteristics. The marine environment has shown to be a very interesting source for new glycosyl hydrolases for both hydrolytic and synthetic aspects. In particular, Aplysia fasciata a marine herbivorous mollusc has been shown to be a potent producer of a library of glycoside hydrolases applied to the synthesis of glycosidic bonds. The impressive assortment of glycosidases in marine organisms clearly indicates that the potential biodiversity of these enzymes is still largely unexplored and that potential applications of biocatalysts from the sea will increase in the near future.     

Effects of Large-Scale Releases on the Genetic Structure of Red Sea Bream (Pagrus major,Temminck et Schlegel) Populations in Japan

Large-scale hatchery releases are carried out for many marine fish species worldwide; nevertheless, the long-term effects of this practice on the genetic structure of natural populations remains unclear. The lack of knowledge is especially evident when independent stock enhancement programs are conducted simultaneously on the same species at different geographical locations, as occurs with red sea bream (Pagrus major, Temminck et Schlegel) in Japan. In this study, we examined the putative effects of intensive offspring releases on the genetic structure of red sea bream populations along the Japanese archipelago by genotyping 848 fish at fifteen microsatellite loci. Our results suggests weak but consistent patterns of genetic divergence (F_ST = 0.002, p < 0.001). Red sea bream in Japan appeared spatially structured with several patches of distinct allelic composition, which corresponded to areas receiving an important influx of fish of hatchery origin, either released intentionally or from unintentional escapees from aquaculture operations. In addition to impacts upon local populations inhabiting semi-enclosed embayments, large-scale releases (either intentionally or from unintentional escapes) appeared also to have perturbed genetic structure in open areas. Hence, results of the present study suggest that independent large-scale marine stock enhancement programs conducted simultaneously on one species at different geographical locations may compromise native genetic structure and lead to patchy patterns in population genetic structure.     

Petroleum biodegradation in marine environments

Petroleum-based products are the major source of energy for industry and daily life. Petroleum is also the raw material for many chemical products such as plastics, paints, and cosmetics. The transport of petroleum across the world is frequent, and the amounts of petroleum stocks in developed countries are enormous. Consequently, the potential for oil spills is significant, and research on the fate of petroleum in a marine environment is important to evaluate the environmental threat of oil spills, and to develop biotechnology to cope with them. Crude oil is constituted from thousands of components which are separated into saturates, aromatics, resins and asphaltenes. Upon discharge into the sea, crude oil is subjected to weathering, the process caused by the combined effects of physical, chemical and biological modification. Saturates, especially those of smaller molecular weight, are readily biodegraded in marine environments. Aromatics with one, two or three aromatic rings are also efficiently biodegraded; however, those with four or more aromatic ring are quite resistant to biodegradation. The asphaltene and resin fractions contain higher molecular weight compounds whose chemical structures have not yet been resolved. The biodegradability of these compounds is not yet known. It is known that the concentrations of available nitrogen and phosphorus in seawater limit the growth and activities of hydrocarbon-degrading microorganisms in a marine environment. In other words, the addition of nitrogen and phosphorus fertilizers to an oil-contaminated marine environment can stimulate the biodegradation of spilled oil. This notion was confirmed in the large-scale operation for bioremediation after the oil spill from the Exxon Valdez in Alaska. Many microorganisms capable of degrading petroleum components have been isolated. However, few of them seem to be important for petroleum biodegradation in natural environments. One group of bacteria belonging to the genus Alcanivorax does become predominant in an oil-contaminated marine environment, especially when nitrogen and phosphorus fertilizers are added to stimulate the growth of endogenous microorganisms.